Public Safety

About Pima County

Selecting Map Features by Area

While there are many ways to select map features using MapGuide, only
methods that "select by area" should be used when working with layers
that have overlapping map features. Selecting by area rather than selecting one
or more individual map features enables MapGuide to drill down through all the
overlapping map features, selecting all the map features in the "stack".

Setting the Selection Mode to "Intersection"

Regardless of the particular "select by area" method you choose, be
certain that your MapGuide Viewer "Selection Mode" is set to
"Intersection". Intersection selection mode ensures all map features
fully or partially within the specified selection area are selected for
reporting. (See Specifyingthe Selection Mode to right-click in the map area, choose Preferences...,
pick "Intersection" in the Selection Mode area and pick OK.) If your MapGuide
Viewer is set to the default "Centroid" (center point) selection mode, then the
center point of each map feature must be within the selection area you specify
to select the map feature. "Centroid" selection mode is not a good choice
because you will not select some map features that are only partially in your
area of interest.

Map appearance after selecting by area may be misleading

Warning: When selecting by area, it may look like some map
features or portions of map features are not selected or are the wrong color
when, in fact, they have been selected properly. This is because selecting a map
feature inverts its color (i.e. the negative of the color). When map features
overlap, there may be two selected map features that both change color,
cancelling the inverted color effect. Also, selecting by area inadvertently
selects map features on all visible layers, even layers that
you aren't interested in, such as layers without overlaps. These selections
interfere visually with the desired selections on the layer with overlaps but
don't affect reports. The report you choose after selecting the map features
only shows entries for the layer(s) the report was designed to support. All
other selected map objects from other map layers are ignored.

In the sample map above, all map features in the displayed area have been
selected.

It's difficult to see what's going on in this sample map because of two
anomalies:

Areas that don't appear to have changed color by being selected actually
have two overlapping improvements plans. Both invert their color, cancelling the
inverted color effect where they overlap. If there were three overlapping areas,
one inverted area's color would not be cancelled and the area would be black.

In this example, street centerlines are also selected as a result of
selecting all map features within the displayed map area. While the street
centerlines are selected they have no affect on the selected improvement plan
areas other than changing the map appearance. Where the street centerlines don't
overlap the improvement plan area, the selected street centerlines display as
bold black lines. Where the street centerlines overlap improvement plan areas,
they are yet another color inversion in the stack.

For the short selected street segment in the top left, there are three
overlaps: The street segment and two improvement plan areas under it.
Each of the three overlap colors invert, but the two selected improvment plan
overlaps color inversions cancel, leaving the one street segment displayed as
selected.

You don't need to understand all this, provided you select your area of
interest, don't try to judge what's selected by color, and use the report of
selected map features (in this case the Improvement Plans report) to identify
and learn more about the plans.

Getting Ready to Select by Area

Zoom in to your area of interest before selecting your map
features of interest. This makes the desired map features easier to see and
select. Zooming in closer means you won't have to squint or have trouble
precisely positioning the mouse.

Turn off Parcels or other layers that are "on top" of your
layer with overlaps before selecting by area. This makes it easier to see what
you are doing prevents selecting parcels that will make it harder to see what
you've selected on your layer with overlaps. (However, if you want to use
"Select features within other map features" below to select all features in one
or more parcels, then you'll need to leave the Parcels layer on.)

Do not select individual map features using the point and click method

Individual map features are selected by single-clicking. Holding down the
shift key while clicking adds the feature to the set of selected map features.
If the feature was already selected, shift-clicking the feature removes the
feature from the selected set.

Clicking on individual map features selects only the "top" map feature. This
is the reason that selecting individual map features should not be used
to select map features to report for layers with overlaps. Selecting individual
map features is useful for many purposes, but not this one!